In vivo antihyperglycemic effect of Ptilostemon casabonae (L.) Greuter leaf extract and its liposomal formulation

Prolonged exposure to hyperglycemia is recognized as the primary factor in the pathogenesis of diabetes, a metabolic disease that affects millions of people and one of the top 10 causes of death globally. Ptilostemon casabonae (L.) Greuter is an edible plant whose extract has recently shown inhibitory activity against α-glucosidase and antioxidant activity. This suggests that this plant could be a candidate to develop natural remedies against hyperglycemia. In this study, the in vivo antihyperglycemic effect of an extract from P. casabonae leaves is presented, and a nanoformulation is proposed to possibly enhance such effect, upon oral administration in rats. Liposomes coated with a gastro-resistant polymer, Eudragit, were developed for the loading and delivery of the extract. Nanosized (ca. 90 nm), unilamellar vesicles were produced, as demonstrated by light scattering results and cryo-TEM micrographs. The effects of the loading of the extract and the coating with Eudragit on the liposomes’ bilayered structure were described by Small-Angle X-ray Scattering. The physical stability of the P. casabonae Eudragit-coated liposomes was evaluated in storage and in simulated gastrointestinal fluids, results showing that the vesicles’ key features were preserved. The vesicles efficiently entrapped rutin (57.4 % ± 5.7) and apigenin (82 % ± 9.1), main flavonoids in the extract, as indicated by the quali-quantitative characterization via HPLC-PDA. P. casabonae extract was found to exert a significant antihyperglycemic effect in rats subjected to a sucrose load, with a reduction in peak glucose level of 33 and 63 % at doses of 40 and 100 mg/kg, respectively. A 10 mg/kg dose of the extract in Eudragit-coated liposomes produced the same reduction (30 %) as that obtained with a 4-fold higher dose of the extract on its own.